The manufacturing techniques of direct-current brushless motor and fan are well-known. Direct-current brushless fan are widely employed in a variety of fields particularly as cooling fan due to low power consumption, low noise, and durability. As such, effort to maintain and further improve such advantages is still desirable.
Conventionally, the smoothness of direct-current brushless motor in rotation is adjusted by manufacturing worker. However, most workers just perform required operations in assembling the work without a sufficient experience to install rotor in a position with respect to stator for obtaining an optimum magnetization. As such, fan may not operate smoothly due to slantingly configured components. A few manufacturers have noticed such problem. However, no document has disclosed techniques to easily assemble rotor and stator in above optimum position.
A conventional technique aiming at eliminating above problem is disclosed. It places washer in shaft housing to adjust the position of rotor with respect to stator. However, the previous design suffered from several disadvantages: 1) Friction may increase due to the insertion of washer which in turn generates noise. An improvement is to fill lubricating oil into shaft housing to reduce friction. But the volumn of oil reservoir is thus decreased. Further, lubricating oil may spill out of shaft housing in operation: 2) Retaining ring is usually employed to secure the end of shaft. Accordingly, retaining ring may rotate when shaft rotates. As such, high friction resistance must exist between retaining ring and shaft in rotation which in turn adversely affects the smoothness of rotation as well as generates noise. Moreover, a rotational resistance to fan still exists in the oil reservoir due to the rotation of retaining ring.
Thus, it is desirable to provide a brushless fan in order to overcome the above drawbacks of prior art.